Can a train move forward too slowly to activate "predictor"?

[Robert_Gift]

I was on a train which reached the crossing before the gates were down because the system was late in detecting forward progress.
Was that a problem with early speed detection systems?

Thank you.

Robert

[TrainmanKight]

I was on a train which reached the crossing before the gates were down because the system was late in detecting forward progress.
Was that a problem with early speed detection systems?

Thank you.

Robert

from what ive seen yes
and if the train starts to pick up speed quickly defiantly. but yah slow train can cause a few problems with the relays most of time the signals will time out and then not restart fast enough, that got fixed as from what ive seen, most island circuits are activation zones no matter the train speed.

[Robert_Gift]

... from what ive seen yes
and if the train starts to pick up speed quickly defiantly. but yah slow train can cause a few problems with the relays most of time the signals will time out and then not restart fast enough, that got fixed as from what ive seen, most island circuits are activation zones no matter the train speed.

Do they even have insulated island circuits in welded rail with crossing predictor devices?

[TrainmanKight]

... from what ive seen yes
and if the train starts to pick up speed quickly defiantly. but yah slow train can cause a few problems with the relays most of time the signals will time out and then not restart fast enough, that got fixed as from what ive seen, most island circuits are activation zones no matter the train speed.

Do they even have insulated island circuits in welded rail with crossing predictor devices?

im sure they do, but im not a signal maintainer or even certified so i really cant tell ya

[Robert_Gift]

... from what ive seen yes
and if the train starts to pick up speed quickly defiantly. but yah slow train can cause a few problems with the relays most of time the signals will time out and then not restart fast enough, that got fixed as from what ive seen, most island circuits are activation zones no matter the train speed.

Do they even have insulated island circuits in welded rail with crossing predictor devices?

im sure they do, but im not a signal maintainer or even certified so i really cant tell ya

Guesses are welcome from those whose specialty this is not.
Hopefully some signal maintainers can answer.

[owensri]

This is really not a likely scenario, due to the fact that the train, doing a speed slow enough to not activate the preditctor on the approach, will activate the crossing on the island regardless of speed. This will be ample warning time alone, because a train going slow enough to not activate the predictor will be traveling 1 mph or less, giving ample time to activate the crossing and give a 20 sec warning.

Now, if a train is sitting say within 200 feet of the crossing, and starts up immediately, and flies towards the crossing at 10 to 15 mph, then of course you are going to get short warning times. It's the train crews responsibility to start up at an acceptable speed to allow the predictor to "realize" the train is moving again, and activate the crossing. For the record, there are no "insulated joint" islands with predictors or motion sensors. What an "island" is, is a high frequency audio signal, that is localized from some point, about 5 to 10 feet past the first set of track wires, to about 5 to 10 feet past the other set of track wires (the wires you see on each side of the roadway). An island circuit is for detecting "occupancy" only, and serves no other purpose.

[cabman701]

An island circuit is for detecting "occupancy" only, and serves no other purpose.

So the island circuit basically is what keeps the signals activated when a train stops and blocks the crossing?

[TrainmanKight]

An island circuit is for detecting "occupancy" only, and serves no other purpose.

So the island circuit basically is what keeps the signals activated when a train stops and blocks the crossing?

Yes the island is an activation zone unless a train clears it signals stay activate
also los (loss of shunt) can also keep signals activate a little longer after the train clears

[AlvinAZ]

It's the train crews responsibility to start up at an acceptable speed to allow
the predictor to "realize" the train is moving again, and activate the crossing.

For the record, there are no "insulated joint" islands with predictors or motion
sensors. What an "island" is, is a high frequency audio signal, that is localized
from some point, about 5 to 10 feet past the first set of track wires, to about
5 to 10 feet past the other set of track wires (the wires you see on each side
of the roadway). An island circuit is for detecting "occupancy" only, and serves
no other purpose.

Cool post. :)

In the old days one big selling point for the predictor was the reduction of
insulated joints. But yeah, seems like the island circuit was to keep the gates
down while a train sat on the crossing but seems like they stretched out far
enough to activate the crossing signals when a train was creeping toward the
crossing.

I never liked predictors. :/

They were all the time acting up because there was no such thing as "perfect
track conditions" which is what they needed to operate right, from what I saw.

Lights on the predictor would tell you whether a train creeping toward a Xing
activated from "prediction" or simply triggered the electronic "island circuit".

Don't remember that stuff all that good from a lack of interest tho. :/

Alvin in AZ